Add -Wredundant-decls to compiler flags.

Makefile

 endif
 
 CFLAGS ?= -O2 -ggdb \
- -W -Wall -Wextra \
+ -W -Wall -Wextra -Wredundant-decls \
  -Wshadow -Wformat-security -Wstrict-prototypes
 
 DEFS = -DBUILD_ID=\"$(BUILD_ID)\" \

tsdecrypt.c

 	return !(!port_set || !host_set);
 }
 
-extern char *optarg;
-extern int optind, opterr, optopt;
-
 static void parse_options(struct ts *ts, int argc, char **argv) {
 	int j, i, ca_err = 0, server_err = 1, input_addr_err = 0, output_addr_err = 0, ident_err = 0, port_set = 0;
 	while ((j = getopt_long(argc, argv, short_options, long_options, NULL)) != -1) {